A medical treatment such as a transurethral ureter lithotripsy or the like is performed for urinary stones generating in a ureter, a renal pelvis, a renal calix and the like (lumens of a living body). In this transurethral ureter lithotripsy, calculus is fractured into a plurality (for example, several tens) of small pieces of calculi by means of a fracturing process such as forceps, shock waves, a laser or the like while viewing calculus with an endoscope (an urethroscope) inserted into a urinary tract, and the plurality of calculi which are fractured and are reduced in size (calculus fragments) are collected with a medical device.
As a medical device configured to collect calculi, for example, as disclosed in Japanese Application Publication Jo. 2008-68102, there is a configuration provided with a basket which can be exposed from a leading end of a sheath. The basket is formed of a plurality of wires. The medical device is inserted into a ureter under an operation of a user such as a medical doctor or the like, the basket is expanded at a location where the calculi exist and catch the calculus fragments into an inside thereof in an expanded state. Subsequently, the user contracts the basket to grasp the calculus fragments, and furthermore, retracts the basket to collect the calculus fragments.